This invention relates to analytical instruments, and more particularly to method and apparatus for determining the nature and characteristics of an unknown substance.
Heretofore, spectroscopists manually studied the spectrum of an unknown substance and, because of their personal knowledge and experience in the field, were able to identify certain characteristics thereof. They would then manually compare the test results with tables of spectra of known substances to determine which substance the unknown one most closely resembled. This was a tedious process and required substantial skill on the part of the spectroscopist.
Thereafter, attempts were made to use mechanical sorters and punched cards for spectral searching. Using the Sadtler spectra, which was the basis of part of the data set contained on the punched cards, one could not even consistently isolate known compounds. There were many reasons for this failure, e.g., sampling conditions were different, instrument calibrations were different, and the operator may not have used the same bands for input data as used by the original encoder of the data.
Attempts have been made to utilize computers to ease the burden of the spectroscopist. Such a system is described in an article by Hugh B. Woodruff and Morton E. Munk appearing in Research/Development, August, 1977 entitled: "Computer-Assisted Infrared Spectral Interpretation". This article describes a system wherein the pattern of peak position, intensity and shape for each of 169 different chemical classes is stored in memory in digital form. The spectroscopist observes the spectrum of the unknown compound under consideration and inputs into the computer the position of the peak maximums and a code number indicating the character of the peak, i.e., broad, average, sharp, strong, medium or weak. The computer then compares this input with each of the 169 classes in storage to output one of five possible confidence levels for each class tested. The article then points out that information from other sources is generally necessary to complete the spectroscopic analysis.